Conventional hybrid vehicles are well known which include an engine and a motor generator for output of a travel driving force to driving wheels (see, for example, Patent Document 1).
The hybrid vehicle of Patent Document 1 is capable of crawling where the vehicle travels while maintaining a very low, constant vehicle speed (e.g., 1 to 5 km/h) to travel off-road and on slippery road surfaces. During crawling, the hybrid vehicle automatically controls the travel driving force output of the engine and the braking force output of the friction brake device collectively, without the driver having to manipulate the accelerator pedal and the brake pedal, in order to maintain a very low, constant vehicle speed. Crawling thus liberates the driver (operator) from manipulation of the accelerator pedal and the brake pedal and allows the driver to concentrate on steering. That alleviates the driver's workload, for example, in off-road driving.
A drawback of crawling is that the braking force output of the friction brake device needs to be frequently increased and decreased during crawling. That will place a heavy load on the friction brake device and likely raise the temperature of the friction brake device. The hybrid vehicle of Patent Document 1 reduces the load on the friction brake device by operating the motor generator as an electric power generator to generate a braking force during crawling. In other words, the hybrid vehicle reduces the braking force output of the friction brake device by utilizing the braking force output of the motor generator as part of the required braking force, thereby being capable of restraining rises in the temperature of the friction brake device.